The world of digital delivery of multimedia content to viewers has been rapidly progressing. Typical types of multimedia content include video clips, electronic games, and interactive content. The delivery process for such multimedia content, particularly those transmitted in a form of video, may entail use of a variety of delivery standards, video quality levels, and other parameters. The techniques used in traditional television (TV) broadcast cannot be effectively used in the more modern multi-standard digital TV arena. Currently, only piecemeal solutions are available for efficient and seamless delivery of such multimedia content, to the arena of digital TV.
Specifically, content delivery is currently performed using two approaches: legacy content distribution and over-the-top (OTT) content distribution. Legacy content providers include, for example, cable, satellite, and internet protocol TV (IPTV) providers. Typically, such providers have full control over the entire delivery chain, from a central location from where the content is originated and transmitted (head-end) through the network to the end user's device (e.g., a set-top box). Therefore, legacy content providers can manage and guarantee efficient content delivery mechanisms and high Quality of Experience (QoE) to the end user.
Over-the-top (OTT) content distribution is the delivery of audio, video, and other types of multimedia content over the Internet without any control of the content distribution by the network operators and/or by the content providers. The providers of OTT content are third party providers which utilize the network's infrastructure to provide content to their subscribers. As such, OTT content providers are not responsible for controlling redistribution of the content. Examples for OTT content providers are Hulu®, Netflix®, and the like.
In most cases, OTT content providers control only the edges of a content distribution network. These edges are streaming servers at the head-end and the media players installed in user devices. However, as noted above, OTT content providers have no control over the distribution network. Rather, such providers merely utilize the network's infrastructure to deliver content. As such, OTT content providers are not responsible for the overall efficiency of OTT content distribution over the network and, as such, cannot guarantee high QoE to their subscribers.
The popularity of OTT services downgrades the performance of the communication networks managed by ISPs. Specifically, OTT content delivery significantly increases the bandwidth consumption in such networks. As a result, ISPs cannot ensure high Quality of Services (QoS) to their subscribers, thereby forcing ISPs to upgrade their networks to support the increased demand for bandwidth. In addition, congested networks cause to higher packets loss and longer packet delays, thereby downgrading the QoE of OTT streaming services.
Broadcast transmissions have been in use around the world for over a century, since the invention of the radio by Marconi in 1895. In broadcast transmissions, a central site such as, e.g., a radio station, transmits content which all users in the network can receive. Multicast transmissions occur when only a certain subset of users in the network can receive certain content. Such situations may occur when, for example, a cable television operator offers a basic package to all of its subscribers, and a premium package (e.g., select sports and/or entertainment channels) that only certain subscribers (e.g., those who specifically pay for such content) can access. In such instances, the basic package is transmitted in broadcast mode, while the premium package is transmitted in multicast mode only to those subscribers who are entitled to the premium package.
In certain environments, there is no limitation on the number of different content items that can be transmitted in a multicast mode. For example, in Internet protocol (IP) based networks running over fiber optics, the number of multicast channels is limited by the theoretical number of approximately 8 million (2^23) multicast addresses, which are either derived from the range of multicast groups supported by IP version 4 (IPv4) addressing mechanisms for multicast (224.0.0.0 through 255.255.255.255) or from the range of multicast group supported by IP version 6 (IPv6) with the prefix ff00::/8, as per the Internet Engineering Task Force (IETF) Request for Comments (RFC) 5771. The IP multicast addresses are mapped to Ethernet multicast addresses in the range 01:00:5e:00:00:00 to 01:00:5e:7f:ff:ff, thereby implying that there are 23 bits of available address space.
The second limiting factor in a network is the total capacity of a physical link to the network. Additionally, fiber optic cables are capable of transmitting data using wavelength division multiplexer (WDM) technology. As a result, the physical link network's capacity also becomes a theoretical limitation. An operator may increase the capacity of the network by a factor of 8—using dense WDM (DWDM) technology. Thus, for practical purposes, a fiber optics operator is not limited in the number of multicast channels it can distribute over its network.
However, there are instances where the number of content items that require transmission in multicast mode is greater than the number of multicast channels available in that network. The immediate implication of such an instance is that a content item that cannot be served in a multicast mode over the network is transmitted to each and every user consuming the content in a unicast mode. Consequently, such transmission causes wasteful usage of the network's bandwidth. An important example of such an instance involves transmissions over cellular networks that have multicast capabilities, such as third generation (3G), long term evolution (LTE) networks, or any other fixed line network with multicast capabilities.
As illustrated in FIG. 1, an LTE radio frame 100 is transmitted once every 10 ms. The LTE frame 100 is sub-divided into 10 sub-frames 1 ms long each. When an enhanced Multimedia Broadcast Multicast Service (eMBMS) is deployed in the network, the sub-frame is the smallest unit that can be allocated to multicast transmissions (see 3GPP TS 36.300 V11.6.0, Section 5). FIGS. 2 and 3 illustrate a LTE frame 200 implemented in frequency-division duplexing (FDD) mode and a LET frame 300 implemented in time-division duplexing (TDD) mode, respectively.
As further illustrated in FIGS. 2 and 3, respectively, the maximum number of allowed sub-frames to be allocated for a MBMS is 6 out of 10 in the case of LTE FDD, or 5 out of 10 in the case of LTE TDD. Significantly, allocating X sub-frames for a MBMS (X is less than or equal to 5 or 6 in the case of TDD and FDD, respectively) reduces the total capacity available for unicast traffic accordingly. Due to these constraints, a tradeoff in the dynamic allocation of multicast resources (e.g., MBMS or eMBMS resources) on a per service basis is crucial for guaranteeing a network's efficiency optimization in a dynamic environment.
FIG. 4 illustrates a multicast content distribution network for streaming multicast content. User equipment devices (UEDs) 410-1 through 410-N are connected in a cellular network 420 via multicast communication channels. In the cellular network 420 implements a multimedia broadcast multicast service (MBMS).
The UEDs 410, which are typically located in a cellular cell site 415, may be part of a network that includes all UEDs in multiple cell sites as part of a multicast broadcast single frequency network (not shown).
A media streaming server 440 generates and delivers media content in multicast streams to the UEDs 410 via several multicast routes 425-1 through 425-M. The media streaming server 440 provides managed OTT content which is owned by a network operator and is delivered by the network operator or through one of its partners. As such, the network operator controls the media streaming server 440 and, therefore, can determine if the delivered content can be multicasted, as well as the number of concurrent viewers of the streamed content.
The MBMS (also known as an eMBMS) is a standardized service which enables broadcast and multicast services of managed OTT content over cellular networks. A MBMS network defines a point-to-multipoint interface for existing and upcoming 3GPP-based cellular networks, such as those defined in the 3GPP standard specifications 3GPP TS 22.246, 43.246, 36.440, 25.346, 23.346, and 22.146. The MBMS is designed to provide efficient delivery of broadcast and multicast services, both within a cell as well as within the core network. For broadcast transmissions across multiple cells, the MBMS defines transmission via single-frequency network (SFN) configurations. Target applications include mobile television and radio broadcasting, as well as file delivery and emergency alerts. Delivery of content over the MBMS requires collaboration between the content owner and/or CDN and the cellular network operator.
One approach to improve the performance of broadband networks providing OTT services is to transmit OTT content or any other type of media content as multicast streams rather than unicast streams. Thus, due to the differences in efficiency of operation of unicast streams and multicast streams in different circumstances, some providers seek to switch from unicast to multicast format streams to minimize bandwidth consumption and improve end users' quality of experience (QoE). However, switching at appropriate times that improve streaming performance in such a manner, typically requires real-time monitoring of various parameters related to streaming content consumption. Furthermore, switching from unicast streams to multicast streams in some cases can downgrade the efficiency of the delivered content. Thus, a decision mechanism should take place in order to improve determine if a media stream, such as an OTT content stream should be delivered as multicast streams.